/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

import java.io.Serializable;
import java.util.LinkedHashMap;
import java.util.Map;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * AttributeAccessors的实现类,该类提供了所有方法的实现.由子类扩展.
 * <p>
 * <p>
 * Support class for {@link AttributeAccessor AttributeAccessors}, providing
 * a base implementation of all methods. To be extended by subclasses.
 * <p>
 * <p>{@link Serializable} if subclasses and all attribute values are {@link Serializable}.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 2.0
 */
@SuppressWarnings("serial")
public abstract class AttributeAccessorSupport implements AttributeAccessor, Serializable {

	/**
	 * 字符串key和对象值的映射
	 * Map with String keys and Object values
	 */
	private final Map<String, Object> attributes = new LinkedHashMap<>(0);


	@Override
	public void setAttribute(String name, @Nullable Object value) {
		Assert.notNull(name, "Name must not be null");
		if (value != null) {
			//有值,则添加
			this.attributes.put(name, value);
		} else {
			//无值,则移除
			removeAttribute(name);
		}
	}

	@Override
	@Nullable
	public Object getAttribute(String name) {
		Assert.notNull(name, "Name must not be null");
		//取值
		return this.attributes.get(name);
	}

	@Override
	@Nullable
	public Object removeAttribute(String name) {
		Assert.notNull(name, "Name must not be null");
		//移除,并返回.
		return this.attributes.remove(name);
	}

	@Override
	public boolean hasAttribute(String name) {
		Assert.notNull(name, "Name must not be null");
		//是否包含指定值
		return this.attributes.containsKey(name);
	}

	@Override
	public String[] attributeNames() {
		//生成名称数组
		return this.attributes.keySet().toArray(new String[this.attributes.size()]);
	}


	/**
	 * 将提供的AttributeAccessor中的所有属性copy到当前集合中
	 * Copy the attributes from the supplied AttributeAccessor to this accessor.
	 *
	 * @param source the AttributeAccessor to copy from
	 */
	protected void copyAttributesFrom(AttributeAccessor source) {
		Assert.notNull(source, "Source must not be null");
		String[] attributeNames = source.attributeNames();
		for (String attributeName : attributeNames) {
			setAttribute(attributeName, source.getAttribute(attributeName));
		}
	}

	/**
	 * @param other
	 * @return
	 */
	@Override
	public boolean equals(Object other) {
		//地址一致,则一致.
		if (this == other) {
			return true;
		}
		//类型不同则不同
		if (!(other instanceof AttributeAccessorSupport)) {
			return false;
		}
		//强转,然后比较关键具体内容
		AttributeAccessorSupport that = (AttributeAccessorSupport) other;
		return this.attributes.equals(that.attributes);
	}

	@Override
	public int hashCode() {
		return this.attributes.hashCode();
	}

}
